1. Field of the Invention
The present invention relates in general to printers, and more particularly to Gravure printers. More specifically, the present invention is concerned with a Gravure printing device which generally comprises a mounting cylinder around which an engraved printing sheet is wound, an ink supplier which feeds a surface of the engraved printing sheet with ink, a doctor blade which scrapes the surface of the printing sheet to remove excess ink therefrom, and an impression cylinder which presses a piece of paper against the surface of the printing sheet.
2. Description of the Prior Art
As is known, Gravure printing is widely used in the field of printing for the print of good quality. Gravure printing is accomplished by engraving and etching various sizes of minute cells (or wells) below the surface of a printing sheet to hold the ink. The engraved printing sheet is wound around a mounting cylinder. After the cells are flooded and loaded with ink, the surface of the engraved printing sheet is scraped of excess ink by a doctor blade. Thus, the leading edge of the doctor blade is kept pressed against the surface of the engraved printing sheet under rotation of the mounting cylinder. The ink remaining in the cells is transferred to the surface of a piece of paper which is pressed against the engraved printing sheet by an impression cylinder.
Due to the nature of such printing process, during a printing operation, paper dust, air dust and the like tend to stick on the surface of the engraved printing sheet. Furthermore, during the printing operation, some of carbon particles contained in the engraved printing sheet become exposed from the surface. Usually, such foreign things are scraped off by the doctor blade together with the excess ink during operation of the printer.
However, due to presence of such foreign things, it sometimes happens that the leading edge of the doctor blade is nicked or chipped to such a severe degree as not to maintain a satisfied ink scraping function. Of course, in this case, the print of good quality is not expected. Usually, the doctor blade is constructed of a ceramic which is harder than the engraved printing sheet. Thus, once the doctor blade is nicked or chipped, the printing sheet is easily damaged.